RDS License showing different expiry date

It is normal for the Per User Remote Desktop Services (RDS) Client Access Licenses (CALs) to show as expiring 60 days after they are issued. Just before their expiration date, if the user logs on, the expiration date will be extended out another 60 days. If the user does not log on before the expiration date, they will drop off the list, but the next time they log on, they will show up again with a new expiration date.

Also, for most license agreements (though not all), 90 days is a more relevant time period because it is the minimum time required before a license can be reassigned to a different person, except under special circumstances. You should refer to the Product Use Rights (PUR), license agreement, or other documents that apply to your specific case for more details​.

https://social.technet.microsoft.com/Forums/en-US/4a3e63b2-e604-48d0-b1b5-d1bc7b1ba203/microsoft-licenses-for-rds-cal-still-show-expiry-date-after-activated-it-is-normal